Which of the following does not change when light travels from one medium to another?

When a ray of light travels from a denser medium to a rarer medium then

Which one of the following statements is correct regarding the travel of a light beam from a rare to a dense medium?

The bending of light as it passes from one medium to another is called:

A ray of light travelling from a rarer medium to a denser medium

Which one of the folowing phenomena verifies the fact that light travels much faster than sound?